What is the ideal refractive index difference for achieving invisibility?

[lanik05]

I was wondering how close 2 refractive Indexes have to be in order to be not visible? I currently have a glass fiber at 1.521 and am researching resin systems to match and so far have 2 - one at 1.506 and the other at 1.4736. I know which one is better (1.506), but is it close enough to "disapear"?

 

[Andy Resnick]

It depends on how sensitive your measurement is. I've used an Abbe refractometer that measured the refractive index down to 0.1% error, and using index-matching fluids I've used differential interference microscopy to observe particles with an index mismatch slightly above that.

Have you talked with Cargille? Another company worth talking to is Norland. Either can help you with your specific application needs better than I.

 

[mpolyanskiy]

You can calculate reflection coefficient using Fresnel equations: http://en.wikipedia.org/wiki/Fresnel_equations"

see also: http://reflectioncoefficient.info/"

 

[lanik05]

Thanks for the inquiries. Is there just a general rule of thumb for how far apart the RI's can be for the majority of materials or is there always other factors that can play a significant role in how well a material will "disapear" into another?